Observations by the Rosetta-Alice Ultraviolet Spectrograph of a Coronal Mass Ejection Impact on Comet 67P/Churyumov-Gerasimenko
Abstract
The Alice ultraviolet spectrograph onboard the European Space Agency's Rosetta spacecraft observed comet 67P/Churyumov-Gerasimenko in its orbit around the Sun for just over two years. Observations taken two months after perihelion, in early 2015 October, show large increases in the Lyman-β, OI 1304, OI 1356, and CI 1657 Å atomic emission lines. Data from the Rosetta Plasma Consortium (RPC) instruments showed a coronal mass ejection (CME) impact at the comet coincident with the emission line increases, suggesting that the CME impact may have been the cause of the increase. Supporting this, the presence of the semi-forbidden OI 1356 Å emission multiplet is indicative of a considerable increase in electron impact emission from the coma and thus an increase in the electron energy and/or density of the plasma, assuming no significant gaseous outbursts occurred at that time. Further, the strength of carbon emission lines does not support either CO or CO2 as significant sources of the oxygen emission. The mechanism responsible for this change to the electron impact contribution could be a product of the interaction between the CME and the coma of 67P. The observed electron impact emission is used to determine the O2 /H2O ratio of the coma at two peaks during the CME event. The exact relationship between the CME and UV emission brightness is not well constrained, but we will present several hypotheses to explain the correlation. This research was made possible by the ESA Rosetta mission with contributions from ESA member states and NASA. The Alice team would like to acknowledge the support of NASA, specifically through JPL contract 1336850 to the Southwest Research Institute.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.P51D2635P
- Keywords:
-
- 6008 Composition;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6023 Comets: dust tails and trails;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6040 Origin and evolution;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6055 Surfaces;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES